1. Field of the Invention
The present invention relates to a mounting structure for a semiconductor device and, in particular, to a chip-on-board mounting structure for a semiconductor device attached to a metallic wiring layer of a metal printed circuit board.
2. Description of the Background Art
In FIG. 1, there is shown a conventional mounting structure for a semiconductor device. A semiconductor device 1 such as a power transistor or the like is mounted to a surface of a metal printed circuit board 2 through solder 6, and the metal printed circuit board 2 includes a metallic substrate 3, an insulating layer 4 which is made of an insulating material such as an epoxy resin, a silicone resin or the like and is formed on the metallic substrate 3, and a metallic wiring layer 5, which is made of a copper foil or the like in a predetermined pattern form and is formed on the insulating layer 4. In this structure, the heat generated by the semiconductor device 1 is transmitted and released to the metallic substrate 3 via the metallic wiring layer 5 and the insulating layer 4.
In this embodiment, the semiconductor device 1 and the metallic wiring layer 5 having respectively different thermal expansion coefficients are tightly connected to each other through the solder 6, and thus a large shearing stress or strain is caused in the solder 6 when the semiconductor 1 generates heat during the operation. As a result, fatigue and failure are caused in the solder 6, and an insufficient contact between the semiconductor 1 and the metallic wiring film 5 occurs.